Think of it as building a foundation of knowledge. You want to build a foundation of how the building blocks of 3d works, and for that you should learn polygon modelling first.
Unless you need the whole model to be double-sided, it's much cheaper performance wise just to duplicate and invert the polygons you need double-sided.
This is not a direct answer, but it should allow you to answer your own question: http://www.rsart.co.uk/2006/11/20/how-many-polygons-in-a-piece-of-string/
In Modo, it's very easy - hit Rotate UVs from the UV tools. It sets the UV coordinates for each vertex to be the UV coordinate of the next vertex of the polygon.